Interpretive Summary: The yellow peach moth is one of the most serious insect pests on maize in China. Because the caterpillars go to dormancy in winter time, the effect of photoperiod and temperature on caterpillar dormancy was examined under laboratory conditions. Short day length caused caterpillars go into dormancy. Critical day length for dormancy induction of the caterpillars was determined as approximately 13 hours at 25 ºC. No specific caterpillar development stage was identified for dormancy induction, but accumulation of 10 day under short day (11 hours of light) was necessary for the induction of caterpillar dormancy. All caterpillars entered dormancy at 20 ºC, and few or none did so at 30 ºC, irrespective of the long- or short-day treatment. Furthermore, under the short day with 11 hours of light, most caterpillars (= 90 %) went into dormancy at 23 and 25 ºC, but a few of them (= 17%) had dormancy at 28 ºC. In contrast, under the long day with 14 hours of light, only a few caterpillars (< 19%) went into diapause at 23, 25, and 28 ºC. This suggested the compensatory effect of temperature and photoperiod on diapause induction in the caterpillars of the yellow peach moth. The ramifications of the experiment in research and management of the maize pest were also discussed.

Technical Abstract:
The yellow peach moth, Conogethes punctiferalis (Guenée), a multivoltine species that overwinters as diapausing larvae, is one of the most serious insect pests on maize in China. Effect of photoperiod and temperature on larval diapause was examined under empirical laboratory conditions. Short-day treatments caused larval diapause at 25 oC, and the critical photoperiod was between 12 and 13 h (or 12 h 51 min) light per day at 25 ºC. No sensitive instar was identified for diapause induction under alternated short- (LD 11:13 h) and long-day (LD 14:10 h) treatments at different larval instars at 25 ºC. However, accumulative treatment of three instars and 10 d under short-day treatment was required for the induction of 50% larval diapause. All larvae entered diapause at 20 ºC, whereas less than 3% did so at 30 ºC, irrespective of the long- or short-day treatment. Furthermore, under the short-day treatment, more than 90 % larvae went into diapause when temperature was less than 25 ºC, but only less than 17% did so at 28 ºC. In contrast, under the long-day treatment, less than 19% larvae went into diapause when temperature was less than 23 ºC. The forward shift (5 ºC) of critical temperature under the long-day regime demonstrated the compensatory effect of temperature and photoperiod on diapause induction.. In conclusion, C. punctiferalis has a temperature dependent type I photoperiodic diapause response; no sensitive larval instar was identified for diapause induction; and the photoperiodic diapause response was also a temperature-compensated phenomenon.